Enlarging a Workbench Top

[Steve Friedman]

Hi all,

I want to lengthen my workbench top by 12" on each end. The top is 24" x 48", consisting of 4 sheets of 3/4" birch plywood laminated to make a 3" top. I planned to laminate (4) pieces of 3/4" birch ply to make a 12" x 24" add-on for each side. I was going to put a 1" hardwood apron around the perimeter and a piece of 1/2" ply on top to hide the seams. My question is how to attach the extension pieces so that the extensions stay attached without sagging.

I waas going to use glue and four 1" dowels, but was not sure if that will be strong enough. Do I need to add steel rods as well? Lag screws? Is this just a stupid idea? Not a big deal to start from scratch, but I don't want to just throw out a 48 x 24 x 3 slab of plywood.

Thoughts?

Thanks,
Steve

[Ben Hatcher]

Put a layer on the top and the bottom. I'd probably do 1/2 on top and 1/4 on the bottom. This would essentially be making a stressed skin panel/torsion box from your existing top. How you attach the wings won't matter much as long as you glue the new skins to the old piece. The skins and to some degree the face will take all of the forces. The slab to slab joint won't see much at all. The 1" dowels won't hurt if you have them and want to use them, too.

If it were me, however, I'd set the old top aside and use a sheet of mdf doubled up, make the skirt boards 1/8 proud of the top, and then add a sacrificial piece of tempered hardboard. You'll get a flatter top that is plenty strong for about the same price as your sheet of 1/2 ply.

[Mike Harrison]

I think I'd do it all. Install the dowels, glue the faces, use pipe clamps above and below to hold it all in place. Once dry, I'd put a piece of half inch on top, then add your border, raised 1/4" for a sheet of masonite to drop into. All the force is "down" so I wouldn't bother about anything on the bottom.

[Steve Friedman]

Thanks. Ben & Mike, You both mention using Masonite as a sacrificial top. I didn't do that on my original bench. Do you glue it down? If so, isn't the Masonite a pain to remove when you want to replace it?

My thought was to do one wing at a time. Part of the reason for doing this is to mount my front vide outside the legs, so I really only need to extend one side about 12". I was going to do the other side only to make the bench look more balanced. Extra space will be nice, but I have two other work areas, so I really don;t need the extra space.

Steve

[Erik Christensen]

if your workbench is only supported on the ends I would junk the top and start all over

if you have lengthwise support I would split in half & put in a new center section kind of like a table leaf

[Ben Hatcher]

No the sacrificial masonite just sits inside the pocket made by the slightly raised skirt boards. It'll normally sit pretty flat without any encouragement. If you're a belt and suspenders guy, you can use a few tiny screws to hold it more securely.

[glenn bradley]

Thanks. Ben & Mike, You both mention using Masonite as a sacrificial top. I didn't do that on my original bench. Do you glue it down? If so, isn't the Masonite a pain to remove when you want to replace it?

I imagine replacement is the plan. I did a worktable that way but 6 years later the top is still fine. I skipped this on my workbench and years later it is still fine as well. I do use the surfaces exclusively for woodworking so there is little to damage them. The occasional deep ding gets filled with epoxy and sanded flush whenever I happen to have batch of epoxy going. I've got 3 or 4 in the workbench top.